1. Field of the Invention
The present invention relates to novel 1-phenylethyl sulfone derivatives substituted by a halogenated alkyloxy group, a process for their preparation and herbicides containing them as an active ingredient.
More specifically, the present invention relates to
(1) 1-phenylethyl sulfone derivatives substituted by a halogenated alkyloxy group, represented by the general formula (I) ##STR2## where R is an alkyl group substituted by a halogen atom, n is 1 or 2, each of P and Q is a hydrogen atom or a lower alkyl group and each of X and Y is a hydrogen atom, a lower alkyl group or a halogen atom;
(2) a process for preparing the 1-phenylethyl sulfone derivatives represented by the above formula (I) which comprises reacting a benzylsulfone derivative substituted by a halogenated alkyloxy group, represented by the general formula (II) ##STR3## where R is an alkyl group substituted by a halogen atom, n is 1 or 2, each of P and Q is a hydrogen atom or a lower alkyl group and each of X and Y is a hydrogen atom, a lower alkyl group or a halogen atom, with a methylation agent, a polar aprotic solvent and a strong base; and
(3) a herbicide containing at least one of the 1-phenylethyl sulfone derivatives represented by the formula (I) as an active ingredient.
The compounds of the present invention represented by the formula (I) are novel compounds having herbicidal activities and exhibit superior herbicidal effects against weeds such as grasses and Cyperus microiria when applied to the soil or foliage treatment. Further, they have a feature that they have little phytotoxicity against broad leaf crop plants such as cotton (Gossypium indicum), soybean (Glycine max), azuki bean (Phaseolus angularis Wight) kidney bean (Phaseolus vulgaris Linnaeus), sugar beet (Beta vulgaris), rape seed (Brassica napus Linnaeus var. oleifera De Candolle), peanut (Arachis hypogaea Linnaeus), sunflower (Helianthus annuus), Japanese radish (Raphanus sativus Linnaeus var. acanthiformis Makino), cabbage (Brassica oleracea Linnaeus var. Capitata Linnaeus), potato (Solanum tuberosum Linnaeus), eggplant (Solanum melongena Linnaeus). Accordingly, they are practically quite useful as an active ingredient of soil treating agents, soil miscible agents or foliage treating agents having selectivity, for broad leaf crop plants. Thus, the compounds of the present invention are most suitable for application to agricultural or horticultural fields, particularly as a herbicide for field application to selectively combat weeds such as grasses and Cyperus microiria for the cultivation of broad leaf crop plants. In addition to the application to the agricultural or horticultural fields such as a up-land field, a paddy field or an orchard, the compounds of the present invention can be applied to combat various weed in noncultivated lands such as a playground, vacant land or railroad sides. Their dosage may vary depending upon the particular site for application, the season for application, the manner of the application, the types of the weeds to be combated or the type of cultivated plant. However, they are usually applied in an effective amount of from 0.05 to 10 kg per hectare.
2. Description of the Prior Art
It is known that a benzylsulfonylpyridine-N-oxide represented by the general formula (III) ##STR4## where R.sup.1 is a hydrogen atom or a C.sub.1 -C.sub.15 alkyl group, Z is a hydrogen atom, a halogen atom, a C.sub.1 -C.sub.3 alkyl group, a nitro group, a cyano group, a C.sub.1 -C.sub.2 alkyloxy group, a --CF.sub.3 group, a 2,2-dichlorocyclopropyl group, a phenyl group, a methylenedioxy group, a vinyl group or a phenyloxy group and m is an integer of from 1 to 5, has herbicidal activities, for instance, from U.S. Pat. Nos. 3,960,542, 4,019,893 and 4,050,921.
Further, it is known from published European patent application No. 36-638 that a benzylsulfonylpyridine-N-oxide represented by the general formula (IV) ##STR5## where R.sup.2 is a hydrogen atom or a methyl group, R.sup.3 is a hydrogen atom, a halogen atom, a C.sub.1 -C.sub.4 alkyl group, a cyano group, a --CF.sub.3 group or a nitro group and R.sup.4 is a hydrogen atom, a C.sub.1 -C.sub.4 alkyl group, a phenyl group or a cyano group, has herbicidal activities.
The the compounds of the present invention represented by the general formula (I) i.e. 1-phenylethylsulfonylpyridine-N-oxide derivatives where a halogenated alkyloxy group is introduced in the benzene ring of the benzylsulfonylpyridine-N-oxide, are not included in the prior art represented by the above general formulas (III) and (IV), and they are novel compounds. Further, it has been found that by the introduction of the halogenated alkyloxy group into the benzene ring of the benzylsulfonylpyridine-N-oxide, the herbicidal activities can substantially be increased and the phytotoxicity against the crop plants can be minimized as compared with the conventional benzylsulfonylpyridine-N-oxide derivatives represented by the general formula (III) and containing an alkyloxy group such as a methoxy group or an alkyl group substituted by a halogen atom such as a --CF.sub.3 group instead of the halogenated alkyloxy group.